1. Field of the Invention
The present invention relates to a discharged fuel diluter having a dilution case in which anode offgas and dilution gas are supplied, diluting the anode offgas by mixing with the dilution gas.
Priority is claimed on Japanese Patent Application No. 2005-198543, filed Jul. 7, 2005, the content of which is incorporated herein by reference.
2. Description of Related Art
A fuel cell mounted on a fuel cell vehicle, producing electric power by performing an electrochemical reaction of reaction gases is known. In this type fuel cell, one having a solid polymer electrolyte membrane, with an anode and a cathode being provided at both faces is known. Fuel gas (such as hydrogen gas) is supplied to the anode and oxidizing gas (such as air containing oxygen) is supplied to the cathode, and the fuel cell produces chemical energy generated by oxidation-reduction of these reaction gases as electric energy.
In this fuel cell, water is generated in the cathode in power generation, and the water partially enters the anode through the solid polymer electrolyte membrane. In addition, a small amount of nitrogen in the air supplied to the cathode enters the anode through the solid polymer electrolyte membrane and is mixed with the hydrogen gas. Impurities in the anode such as the water and the nitrogen have the potential to make the power generation of the fuel cell unstable.
Especially in a circulation-type fuel cell system in which unreacted hydrogen discharged from the fuel cell (anode offgas) is mixed with fresh hydrogen gas for recycling and supplied to the fuel cell again for improving fuel utilization, the concentration of the aforementioned impurities in the anode increases with operating time.
In this type fuel cell, the anode offgas containing the impurities is discharged from an anode offgas line in which anode offgas circulates by opening a discharge valve at regular intervals. The concentration of the impurities is thus lowered.
Before discharging anode offgas outside of the fuel cell (into the air), the hydrogen concentration of the anode offgas is lowered by diluting with the dilution gas (e.g., air as cathode offgas which is discharged from the cathode).
Japanese Unexamined Patent Application, First Publication No. 2002-289237 discloses a treatment equipment of the related art. This discharged gas treatment equipment introduces a portion of the cathode offgas to a dilution case, dilutes the anode offgas in the dilution case in portions, and discharges the diluted anode offgas outside of a vehicle in portions.
As shown in Japanese Unexamined Patent Application, First Publication No. 2002-289237, it is preferable to constitute gas passage meandering by providing shields (partitioning members) in the case of a discharged fuel diluter, because dilution efficiency can be improved by making the gas passage longer while maintaining the volume of the case.
However, when the partitioning members are thin and have low rigidity, they vibrate due to the gas introduced in the case. This causes noise and lowers diluting performance by disturbing the gas flow.
Though making the partitioning members thicker is a possible solution to this problem, this increases the weight of the partitioning member. In addition, since the volume of the members also increases, the dilution case must be larger to maintain the volume of the gas passage therein. In the related art, securing the partitioning member's endurance has been an obstacle to weight reduction and downsizing of the diluter.